Evaluation of energy expenditure has become an indispensable tool for studies involving lean and obese mice. Systems capable of such evaluation are commercially available and can monitor activity, oxygen consumption, CO2 production, feeding and drinking. From this data respiratory quotient, RER and heat produced can be calculated. However the systems are expensive and sophisticated. The Endocrine Division at BIDMC has a sixteen animal monitoring system purchased by outside funds. To make the technology available to PPG investigators, monitoring is offered as a core service. Following monitoring data is provided to the requesting investigator as Excel spreadsheets and graphs plotting the variable of interest in real time. The core assists in experimental design and data analysis. An additional service of the core is assistance with DEXA monitoring for PPG projects.